scanf error handling C

Question

Say If i want an input to be

[Name] [Name]

How would I detect

[Name] [Name] [Name] 

and return error?

Answer 1

scanf returns the number of validly converted arguments. So in your first case, the return value would be 2, in the latter case 3.

To check the right amount of parameters, this might help:

char in[20];
char out[20];
char error[20];
int check;

check = scanf(" %s %s %s", out, in, error);
if(check != 2)
{
    // TODO: error handling
}

EDIT: now it should be working, see comments below.

Of course, as stated by other posters: scanf is not considered a quite safe function since buffer overflows can occur, and you should avoid using it. It is better to read the inputs to a buffer with fgets() and the try to parse the arguments you want.